The present invention relates to a connector for electrically connecting coaxial cables and, more particularly, to a receptacle capable of electrically connecting cable conductors of a large variety of different diameters, including those of coaxial cables of large current capacity (usually 3A or larger) and small current capacity (usually up to 3A).
The reliability of a system constituted by coaxial cables which inherently has a good transmitting characteristic is largely affected by the reliability of a number of connectors used in the system for connecting these coaxial cables. From this point of view, research and development of technics for improving the reliability of these connectors have a substantial significance.
In practical design of the system making use of the coaxial cables, coaxial cables having cable conductors of suitable diameters are selected from a group of commercially available coaxial cables having cable conductors of diameters which differ over a wide range of between 0.5 mm and 1.8 mm, in accordance with the difference of the current capacities. It is therefore necessary, in order to obtain a sufficiently high reliability of the system, to develop a new receptacle which can accomodate itself to the difference of diameters of cable conductors which are usually 0.5 mm to 2 mm.
Under this circumstance, F type or FN type connectors have been developed for connecting coaxial cables of current capacity of up to 3A, while fitting type connector has been developed for use in combination with coaxial cables having current capacity exceeding 3A, and these connectors have been selectively used in accordance with the condition of use.
Thus, the fitting type connector is used when a relatively large current capacity is required at the connection. This type of connector is fixed by at first inserting the cable conductor into the electric device and then pressing the cable conductor onto the fitting seat by means of screws. Accordingly, the attaching of this type of connector requires a troublesome work of unsealing of the electric device and the pressing of the cable conductor by means of screws.
In case of a female receptacle, which is adapted to be incorporated in the electronic device or in the connector as in the case of the fitting seat, the cable conductor or a contact pin connected to the cable conductor is directly inserted into the device from the outside of the latter, so as to accomplish the required electric connection. Thus, the troublesome task of unsealing the electric device is conveniently eliminated by the use of this female receptacle so that the connection can be accomplished very easily.
In order to enjoy the described merit of the female receptacle in general cases, however, it is necessary that the female receptacle has advantages equivalent to those offered by the fitting seat, i.e. the stability against mechanical vibration or oscillation, increment of the current capacity and the accommodation or adaptation to the difference of diameters of cable conductors. Further, in order that the receptacle satisfy these requirements, the spatial dimension allotted to the receptacle is as small as 30 mm in axial length and 3.times.3 mm.sup.2 in cross-sectional area. The restriction imposed on the mechanical processing of constituents of the receptacle which is to be accommodated by such a limited space is extremely severe. Any excessive construction deteriorates the practicability. It is therefore necessary to develop a receptacle having a novel construction over the prior art which can fulfill the above-stated requirements.
The specification of U.S. Pat. No. 3,838,388 discloses a branch-type contact which is characterized by having opposing resilient arms for obtaining a contact pressure, in which a pair of parallel recesses extending in the axial direction and curved in the cross-sectional direction of the resilient arms are formed. At the same time, a resilient retaining member is disposed between two branches and bent in the direction opposite to the direction of contact, so that the resilient retaining member may appear between the branches when the contact is attached to a terminal block. This retaining member, however, has no function of making electric contact with the cable conductor or contact pin, because it does not exert any clamping force.
The pair of resilient arms having parallel recesses, disposed such that these recesses oppose each other, is advantageous in that they provide a recessed guide space for guiding the male pin when the latter is inserted. The increment of the contact pressure on the male pin, offered by the curvature of the recesses is, however, rather incompatible with the adaptability of the receptacle to the variation of sizes of coaxial cables with which the present invention is concerned.
Namely, a reinforcing structure having a pair of parallel recesses of, for example, 3 mm wide formed over the entire length of the linearly declining resilient arms. However, this reinforcing structure on the other hand narrows the range of resilient deformation of the arms, resulting in poor adaptability to the variation of size of the male contact.